The major objective for this project is to investigate the mechanisms by which mammalian sperm are capacitated and undergo the acrosome reaction in vivo. Particular attention is being directed toward detection and characterization of chemical changes in the lipids and proteins of the plasma membrane of sperm during exposure to the secretions of the female reproductive tract. The pig is the primary experimental animal. The lipids (phospholipids, neutral lipids and sterols) of plasma membrane will be studied before and after incubation in utero. The hydrophobic side chains of the lipids will be analyzed as well as the individual lipid types. The identification and characterization of the proteins exposed on the surface of sperm will be continued. The contribution of seminal plasma proteins to the surface coating and the effect of incubation in utero will be examined. BIBLIOGRAPHIC REFERENCES: Esbenshade, K.L., and E.D. Clegg. 1976. Electrophoretic characterization of proteins in the plasma membrane of porcine spermatozoa. J. Reprod. Fert., 47, 333. Clegg, E. D. 1975. Preservation by freezing of animal cells and tissues. ASHRAE Journal, Dec. issue, p. 23.